As is described in our above-referenced co-pending parent application Ser. No. 906,772, now U.S. Pat. No. 4,178,485, issued Dec. 11, 1979, and assigned to the assignee of the present application, line circuits, such as those associated with an electronic PBX have particular characteristics and requirements among which are the ability to change signal levels, provide balanced line to unbalanced line conversion, etc. For a detailed discussion of such line circuits, attention may be had to our above-referenced application, which application is incorporated by reference in the present application.
As is discussed in detail in our copending parent application, we have already developed a line circuit that contains a two to one wire bidirectional amplifier arrangement which transforms a balanced tip and ring circuit to an unbalanced line and, at the same time, transforms an unbalanced line to a balanced lead pair. A detailed schematic diagram of the circuitry configuration for implementing such a line circuit is depicted in FIG. 2 of the above-referenced application.